Connecting GRBs from Binary Neutron Star Mergers to Nuclear Properties of Neutron Stars

TL;DR

This paper links the observed ratio of long to short gamma-ray bursts from neutron star mergers to the neutron star equation of state, constraining the threshold mass for remnant stability and providing insights into nuclear physics scenarios.

Contribution

It introduces a novel method to estimate the threshold mass for neutron star remnant collapse using gamma-ray burst observations, connecting astrophysical data with nuclear physics models.

Findings

Current data favor a high threshold mass $M_{ls} \, \simeq \, 1.3 M_{TOV}$.

Results suggest the maximum neutron star mass $M_{TOV} \lesssim 2.6 M_\odot$.

Nuclear physics scenarios with rapid collapse at a few times nuclear density are disfavored.

Abstract

The fate of the binary neutron star (NS) merger remnants hinges sensitively upon the NS equation of state and the threshold mass, $M_{\rm ls}$, that separates a long-lived from a short-lived NS remnant. The nature of the electromagnetic counterparts is also influenced by the remnant type, particularly in determining whether a gamma-ray burst from a compact binary merger (cbGRB) is of short or long duration. We propose a novel approach to probe $M_{\rm ls}$ by linking it to the estimated observed ratio of long to short cbGRBs. We find that current observations broadly favour a relatively high value for this transition, $M_{\rm ls}\simeq 1.3 M_{\rm TOV}$, for which $ M_{\rm TOV} \lesssim 2.6\,M_\odot $, consistent with numerical simulations, as also shown here. Our results disfavour nuclear physics scenarios that would lead to catastrophic pressure loss at a few times nuclear density and temperatures of tens of MeV, leading to a rapid gravitational collapse of binaries with total mass $M \lesssim 1.3 M_{\rm TOV}$. Future individual gravitational wave events with on-axis cbGRBs can further bound $M_{\rm ls}$.